1. Field of the Invention
This invention relates generally to telephone answering systems, and more particularly to a programmable telephone interface device which can be programmed to perform various operations responsive to user input dual tones and CNG signals.
2. Brief Description of the Prior Art
There are a number of telephone answering systems and facsimile apparatus which will automatically switch an incoming call between a telephone or a facsimile machine and will allow a caller to choose to be connected to a specific telephone extension by pushing one or more keys on a standard touch tone telephone keypad.
Hashimoto, U.S. Pat. No. 4,584,434 discloses a system wherein a telephone answering device (TAD) is activated upon receipt of a ringing signal to send an outgoing message (OGM) and thereafter the calling party must leave a message or enter a code by pressing touch tone buttons to activate a facsimile machine. The device requires input by the calling party and is therefore not substantially automatic.
Bowen, U.S. Pat. No. 4,910,764 discloses a facsimile and voice communications device which allows a telephone and facsimile machine to share a common telephone line. The device answers the telephone and listens for a calling signal (CNG) and will automatically default to a facsimile machine upon receiving a CNG signal. It can also respond to touch tones, however it is only capable of connecting to a facsimile machine and allows hang-up only after detecting a dial tone which ties up the system before resetting. It also does not provide a true dual tone decoder.
Hashimoto, U.S. Pat. No. 4,974,253 discloses a facsimile apparatus incorporating a telephone answering machine. The device has a digital outgoing message (OGM) with a calling signal (CNG) interrupt and can receive dual tone (DTMF) manual inputs, however the discriminating signal is the handshaking signal CNG of a calling facsimile machine and it only responds to an incoming call after the answering machine has finished the outgoing message.
Bowen, U.S. Pat. No. 4,910,764 discloses a central interface telephone answering unit and a series of remote units connected therewith which answers the telephone and listens for a calling signal (CNG) and will automatically default to a facsimile machine upon receiving a CNG signal. Each of the remote units responds to a predetermined tone frequency and when the caller pushes a touch tone key, to select a specific extension, the responding remote unit generates a ringing signal for that extension. The central unit resets when a dial tone is detected after a caller hangs up or when a remote extension completes the call.
The present invention is distinguished over the prior art in general, and these patents in particular by a programmable telephone interface device which connects to a telephone subscriber line and automatically controls the operation of facsimile equipment and telephone equipment connected to the device. The device includes a microprocessor having stored programs in memory for receiving and interpreting digital signals. Ports on the device allow connection of at least one telephone, a telephone answering device, and a facsimile machine. One or more outgoing messages can be recorded and stored in memory. An AC ringing voltage on the subscriber line representing an incoming telephone call is detected by a ring detection circuit and a DC pulse detection circuit detects changes in the current on the telephone subscriber line representing pulse dials, off-hook signals, and canceled calls. Facsimile transmission (CNG) signals and dual tone multi-frequency (DTMF) tones are filtered, decoded and converted to digital signals by a filter and decoder circuit which are interpreted by the microprocessor. The microprocessor selects a port corresponding to the type of signal detected and causes a ring voltage signal to be generated to activate the telephone equipment or facsimile machine connected to the selected port. The ring voltage signal is sent to the facsimile port if the detected signal is a CNG signal or a predetermined DTMF tone representing the facsimile port, or is sent to the telephone port or the telephone answering device port if a CNG signal is not detected or if the detected signal is a predetermined DTMF tone representing a particular port.